1. Field of the Invention
The present invention relates to a method of fabricating a carrier. More particularly, the present invention relates to a method of fabricating a film carrier.
2. Description of Related Art
With the great advance in the electronics industry, many types of multifunctional electronic products have become indispensable in our daily life. Most electronic products are driven or controlled by integrated circuits on a die. To protect the structurally weak die and facilitate reliable signal transmission, the die is generally enclosed within a package. In the past, many types of chip packages have been developed. The most common chip bonding techniques include wire bonding (W/B), flip chip (F/C) bonding and tape automatic bonding (TAB). In the TAB technique, a silicon chip is bonded to a film carrier. Since the chip is bonded to a thin film, the TAB package is slim, light, flexible and easy to install.
FIGS. 1A through 1J are schematic cross-sectional views showing the progression of steps of fabricating a conventional film carrier. First, as shown in FIG. 1A, a film 100 is provided. Next, an adhesive layer 110 is formed over the film 100. As shown in FIG. 1B, the film 100 is punched using a cutting tool (not shown) to form a plurality of holes 102 in the film 100. The holes 102 are, for example, sprocket holes used for driving the film 100 forward in a subsequent automatic bonding process or device holes. As shown in FIG. 1C, a metallic layer 120 is laminated on the film 100. Through the adhesive layer 110, the bonding strength between the film 100 and the metallic layer 120 is enhanced.
As shown in FIG. 1D, a flex coating material is deposited into some of the openings 102 to form a flex coat layer 130 that permits the film 100 to flex along the flex coat layer 130. As shown in FIG. 1E, a first photoresist layer P10 having a plurality of opening 01 thereon is formed over the metallic layer 120. In the meantime, a second photoresist layer P20 is formed on the surface of the film 100 away from the metallic layer 120. As shown in FIG. 1F, using the first photoresist layer P10 as an etching mask, a portion of the metallic layer 120 is removed so that the metallic layer 120 is patterned to form a plurality of metallic leads 122. Thereafter, the first photoresist layer P10 and the second photoresist layer P20 are removed to form the structure shown in FIG. 1G.
As shown in FIG. 1H, a first tin layer 140 is formed on the surface of the metallic leads 122. Next, as shown in FIG. 1I, an anti-soldering layer 150 is formed on the surface of a portion of the first tin layer 140. Thereafter, as shown in FIG. 1J, a second tin layer 160 is formed on the remaining surface of the first tin layer 140.
In the conventional method of fabricating film carrier, holes are cut using punching tools. Since the size and location of the holes in the film carrier are different for each batch of chips, a different set of cutting tools has to be made for the production of a fresh new batch of products. In other words, excessive time and labor are needed for fabricating necessary cutting tools, thereby increasing the cost of the film carrier. Furthermore, the metallic layer is formed on the film after holes are fabricated on the film. Hence, the metallic layer may have some unevenness around the openings.